CREATING ACCOUNTS Figure 6-4: Unionbank Accounting Files
8.2 FILE MIGRATION
Some installations must control the use of disk space by periodically
TAPE STORAGE
migrating files to magnetic tape. This forced file migration allows the management of an installation to move old unused disk files to a less expensive storage medium. Similar to archived files, migrated files are still easily accessible to the user. File migration also allows you to keep users' directories below their permanent allocation. (Refer to Section 5.5 for a description of permanent and working storage allocations.)
Whether you use the file migration facility depends almost entirely on your disk space resources. If users are archiving files regularly, if their directories are usually below their allowed permanent disk allocation, and your system is not continuously interrupted with "disk space low" messages, you may choose .not to migrate files. Otherwise, if you are constantly receiving the [CAUTION - DISK SPACE LOW ON structure name] message, you may want to forcibly migrate files from the disk.
Sections· 8.2.1 through 8.2.3 describe using file migration. They include:
o the program you must run before migrating files to tape
o the command that can be placed in the n-CONFIG.CMD file to change the default tape recycle period
o when to run the REAPER program that marks files for migration and marks for deletion the contents of archived and/or migrated files
o a sample of the
REAPER.CMD
file that you can use as a default file to be read by the REAPER programo when to run the DUMPER program that locates files marked for migration and copies them to tape
o when to process retrieval requests for migrated files o when to recycle migrated (and archived) tapes
8.2.1 Setting Up the System to Use File Migration
When you receive the TOPS-20 Installation Tape and have brought up the new TOPS-20 monitor, your system contains a built-in default of 180 days for recycling migrated tapes. This default is placed in the FDB of each file as it is migrated to tape.
To change the 180-day default, you can enter a command in the n-CONFIG.CMD file to inform the system when you plan to recycle your migrated tapes. This command is:
8-8
TAPE STORAGE
TAPE-RECYCLE-PERIOD days
Select a length of time that is appropriate for your installation.
The default of 180 days, however, is a standard time period. You can place the TAPE-RECYCLE-PERIOD command in the n-CONFIG.CMD file at the time you install the system (refer to the !Qr§:~Q ~~ MQQ~! ~
!~~~~!!~~!Q~ g~!Q~). Or, you can edit the n-CONFIG.CMD file at a later date. Remember that if you edit the file at a later date, you must reload the system to process the commands in the n-CONFIG.CMD file.
CAUTION
If you decide to change the 180 day default, place the TAPE-RECYCLE-PERIOD command with the new argument in the n-CONFIG.CMD file and reload the system.
Otherwise, the default recycling period does not change until·the next system reload.
·8.2.2 Using the REAPER Program
The REAPER program is the tool used to free disk space.
the following functions:
It performs
o Marks for migration the files that have not been referenced for a specified period of time
o Marks for deletion the disk contents of archived or migrated files, either after they have been successfully copied to tape, or after they have been returned to disk with the RETRIEVE command, and have not been referenced for a specified period of time
o Trims directories that are over permanent disk allocation by marking files in those directories for migration
o Deletes (purges) the tape pointers in FDBs on the disk that have reached their tape storage expiration date. That is, the file's FDB will no longer contain a pointer to the contents of the file on tape.
You can instruct the operator to run the REAPER program and perform one, several, or all of these functions. The operator can give a list of commands to REAPER or use the TAKE command with the default argument SYSTEM:REAPER.CMD. After the system is installed, the directory <SYSTEM> contains a default REAPER.~ID file. You can use this file as it is or use an editor and change the default parameters.
The default SYSTEM:REAPER.CMD file appears ~imilar to the following.
$TYPE (FILENAME) SYSTEM:REAPER.CMD<RET>
TAPE STORAGE
!Directories over perm allocation
!back to perm allocation when running the REAPER program; otherwise, you may accidentally migrate some very important files from the disk. You can use more
The REAPER program accepts the following commands.
BEGIN (Processing files)
DELETE-CONTENTS (Of old offline files) EXIT (To monitor)
TRIM (Directories over allocation)
The
IQe§=gQ
Q2~r!~Qr:~ g~!~~ provides a complete description of all the commands that can be given to the REAPER program or placed in the REAPER.CMD file. Typically, you .give a number of commands to REAPER, one for each operation you want performed.8-10
TAPE STORAGE
The availability of disk space determines how often you run the REAPER program. If your disk space is low, you may want to run the REAPER program daily to free up as much disk space as possible. Other installations may run it once a month or less.
8.2.3 Using the DUMPER Program
After the REAPER program marks files for migration, the operator runs the DUMPER program to copy the files to tape. Similar to an archived file, a migrated file is not completely migrated until two copies of the file exist on magnetic tape. Section 8.1.4 describes a procedure for copying archived files to tape. You can use this same procedure for migrated files, by using the MIGRATE command instead of ARCHIVE.
If you use both the file archiving facility and the file migration facility, do not merge archived and migrated files on the same tapes.
The expiration dates for migrated files differ greatly from the expiration dates on archived files. If you put them on the same tape, you will end up saving migrated files for approximately ten years and use up all your tape resources very quickly.
8.2.4 Processing Retrieval Requests for Migrated Files
When a user gives a DIRECTORY command, the files that have been migrated to tape still appear in the directory list; however, each file has a notation (;OFFLINE) beside the filename to indicate that the file is contained on tape and not on the disk. The versions of migrated files that have been copied to tape can be returned to disk, and unlike archived files, they can be altered and/or renamed in the ordinary manner. The user requests that a migrated file be returned to disk with the RETRIEVE command. These requests are stored in the same queue as archive requests until the operator processes the queue.
The TQe§=~Q QE~r~~Qr~2 g~!g~ describes how to process retrieval requests. Retrieval requests for migrated or archived files should be processed frequently.
8.2.5 Recycling Migration (and Archive) Tapes
When all the migrated or archived files on a tape have passed their expiration dates and all pointers to these files on the disk have been deleted, you can recycle the tape.
The PURGE command to REAPER checks tape expiration dates and notifies users by the MAIL program when migrated or archived files on tape are about to expire. Users can retrieve the file to disk again or discard the tape pointer on disk if they no longer need the file.
TAPE STORAGE
The operator can determine if a tape can be recycled by giving the TAPE command to REAPER. If a tape is not mentioned in the TAPE output list, this means that none of the disk structures that ate on-line at this time and specified to REAPER contain FDB pointers to that tape.
However, be sure that you check all possible places for on-line (disk) pointers to this tape. That is, run REAPER with the TAPE command on all the disk structures on all systems that may contain pointers to this tape. If files have passed their expiration date and pointers to them still exist on the disk, the operator can run REAPER with the PURGE command to delete these pointers. The operator should be certain that files are no longer needed before using the PURGE command.
HINT
When a migration tape is full, have the operator use the PRINT command to DUMPER to obtain a hard-copy listing of the tape contents.